1. The Field of the Invention
This present invention relates generally to decorative resin panels and processes, for use in decorative and/or structural architectural applications.
2. Background and Relevant Art
Recent trends in building design involve using one or more sets of decorative panels to add to the functional and/or aesthetic characteristics of a given structure or design space. These recent trends are due, at least in part, because there is sometimes more flexibility with how the given panel (or set of panels) is designed, compared with the original structure. For example, recent panel materials include synthetic, polymeric resin materials, which can formed as panels to be used as partitions, walls, barriers, treatments, décor, etc. Examples of such resin materials include polyvinyl chloride or “PVC”; polyacrylate materials such as poly (methyl methacrylate) or “PMMA”; polyester materials such as poly (ethylene-co-cyclohexane 1,4-dimethanol terephthalate), or “PET”; poly (ethylene-co-cyclohexane 1,4-dimethanol terephthalate glycol) or “PETG”; glycol modified polycyclohexylenedimethlene terephthalate; or “PCTG”; as well as polycarbonate; or PC materials.
In general, resin materials such as these are now popular compared with decorative cast or laminated glass materials, since resin materials may be manufactured to be more resilient and to have a similar transparent, translucent, or decorated appearance as cast or laminated glass, but with less cost. Decorative resins can also provide more flexibility compared with glass at least in terms of color, degree of texture, gauge, impact resistance, and ease of fabrication. One conventional method of coloring a resin panel includes adding colorants as the resin panel is extruded. Other techniques include the use of dye sublimation.
For example, dye sublimation involves first imparting an image or decorative design on a dyestuff (i.e., dye carrier) with sublimation inks. The image or decorative design is typically imparted on the dyestuff by an inkjet or a laser printer. After the image is imparted on the dyestuff, a manufacturer places the dyestuff on the substrate (object on which the image is to be printed). There are a number of different ways that the manufacturer can then sublimate the dye into the given substrate.
In one conventional example, the manufacturer places the assembly into an oven, and heats the assembly above the sublimation temperature of the dye and the glass transition temperature (“Tg”) of the substrate. In this case, the manufacturer positions the assembly so that the oven's heat source provides heat directly to the side of the substrate to be decorated (i.e., via dye sublimation). In most if not all cases, the manufacturer also applies continuous pressure. Once the dye reaches its sublimation temperature, and the substrate has reached its Tg, the dye infuses into the substrate, thus importing the intended image to the substrate. Thereafter, the manufacturer cools the assembly to a temperature below the Tg of the substrate.
In another conventional process, the manufacturer uses vacuum bags or the like to aid in the distribution of pressure. For example, the manufacturer may place the dyestuff and substrate assembly into a vacuum bag. Similarly, a manufacturer can position a substrate and dyestuff within a pliable covering membrane that has dimensions greater than the substrate. In both cases, the manufacturer can then evacuate the air from the assembly. In the membrane example, the manufacturer evacuates air from the covering membrane through a perforated platen placed below the substrate. After removing pressure in this manner, the manufacturer then positions the vacuum bag assembly in an oven so that the oven's heat source applies heat primarily to the side of the assembly containing the dyestuff/dye carrier.
Unfortunately, each of the above-described conventional sublimation processes result in warping of the substrate to greater or lesser extents, even though prevention of warping is sometimes identified as an objective. One reason for this is that conventional methods and apparatus only or primarily heat one side of a given assembly at a time—the side on which sublimation is intended. Specifically, heating the substrate primarily or exclusively on one surface/side of a substrate can cause a non-uniform temperature gradient across the thickness or gauge of the substrate. Moreover, the effect of the uneven temperature gradient can be exacerbated when the manufacturer attempts to further sublimate dye into a second (e.g., opposing) side of the resin substrate. That is, when the manufacturer turns the resin substrate over to sublimate dye on another side of the resin substrate, the resin substrate will be subjected to an uneven temperature gradient for a second time. The renewed uneven temperature gradient on the additional, opposing side can further warp the overall panel as before, and still further distort the already-sublimated dye image on both the original side as well as on the new image side.
With relatively small and inexpensive plastic-based applications, such as photographic papers or films, thin plastic sheets, toys, or appliance components, the uneven temperature gradient in the substrate is not much of a concern, and the effects of the temperature gradient may not be too noticeable. This uneven temperature gradient, however, can be more problematic with higher-end, engineered thermoplastic substrates, that are much larger (e.g., 4′ wide×8′ long) and thicker (e.g., ¼″, ½″, and 1″ gauge), such as those used as decorative architectural resin panels prepared with specific structural and aesthetic ends in mind for use in high-end building applications. Specifically, the resultant uneven temperature gradient experienced in sublimation printing of these higher-end substrates can cause disproportionate surface stresses in the resin panel, which ultimately can cause the resin panel to bow, warp, or curve. This particular warping from uneven heat can render the substrate unsuitable for its shape alone, especially when installed in a frameless application, not to mention unsuitability due to distortion of the image being sublimated.
In addition, the pressure created by the vacuum bag, or covering membrane on a platen, when combined with the heat needed to cause dye sublimation, tends to further deform the substrate by rounding the edges and corners of the substrate. Specifically, conventional vacuum-based methods tend to result in pinching and subsequent rounding of the edges of the plastic substrate to conform to the contours of the vacuum bag or covering membrane. One will thus appreciate that there are thus multiple, significant disadvantages with applying conventional dye sublimation processes to substrates where flatness, surface uniformity, and optical properties such as image crispness and alignment are at a premium for at least these reasons.
In addition to these disadvantages, conventional methods can further require long processing times that may make such methods expensive or even commercially unviable for large architectural panels. For example, conventional methods typically involve heating and cooling the substrate within the same processing unit in order to keep the substrate under continuous pressure. Thus, a manufacturer usually needs to afford time to cool the processing unit, and then heat the processing unit up again in anticipation of processing the next substrate. Although conventional processing times for heating and cooling the same processing unit may be appropriate for smaller, thinner items, where many such items can be placed in the same unit, or where large-scale manufacturing is not a concern, such processing times would be inefficient and prohibitively costly for use with substrates that are much larger (e.g., 4′ wide×8′ long), and thicker (e.g., ¼″-1″ thicknesses), particularly where large-scale manufacturing is desired.
Accordingly, there are a number of disadvantages in conventional methods for dye sublimation printing on resin substrates that can be addressed.